Sliding seal arrangements between relatively movable members are well known and are particularly useful in high performance gas turbine engine exhaust nozzles wherein one or more flaps move adjacent a stationary sidewall for directing the engine exhaust gases or varying the nozzle outlet area. Such sliding seals must not only resist the elevated pressure of the exhaust gases, up to 35 psig or higher, but also must resist temperatures which can reach over 4,000.degree. F. (2,200.degree. C.) for an engine and operating afterburner arrangement.
One complication in attempting to provide a sliding seal for members in such a nozzle arrangement is the occurrence of uneven warpage or other displacement between the nominally planar sidewall and the movable flap. Under the influence of uneven gas static pressure and temperature, sidewalls and flaps in modern lightweight nozzle arrangements can warp or flex unevenly over the length of the desired sealing line, requiring a seal assembly able to accommodate local variations in displacement between the members.
Prior art seals utilizing a continuous sealing element must be relatively flexible along the length of the seal assembly to allow the assembly to accommodate such differential displacement. Such flexibility is at odds with the requirement that the sealing element withstand the pressure loads and have little distortion due to exposure to high temperatures. These requirements typically indicate a thicker and hence a more inflexible sealing element is necessary. Prior art designs, for example U.S. Pat. No. 4,575,099 issued to Nash, have attempted to balance these needs through the use of a hinged, continuous sealing element. As with any continuous element, the ability to accommodate variation in the displacement between the members along the desired sealing line is related to the flexibility of the sealing element and attendant structure. What is required is a sliding seal assembly able to achieve the desired sliding seal with strong, relatively inflexible seal elements.